ESD Ball Valve material

[cam72]

Ball Valve material

In ongoing project we are procuring ESD ball valves of various class ratings i.e. 300 onwards up to 1500#. Client specification for ball material is ASTM A182 F316L or A351 –CF8M. Vendor from whom we are procuring these valves is unable to give this ball material for class 600# and above. Vendor says for class 600# and above SS is soft. Argument given by vendor is during hydro test pressure (1, 5 times) SS 316 may not withstand hydro test pressure. (220 bar hydro test pressure or more for class 600# and above). I want to know is it really a fact that for class 600# and above SS 316 can not be used as a ball material? Somehow, I am not convinced with this vendor argument and trying to go through various standards to check his claim. Want to know opinion from this forum. thanks.

 

[bcd]

As a general statement, the vendor arguement that the material is too "soft" for higher pressures is not true at all. Class 4500 valves can be from F316L and CF8M. However, it is most likely true for the design of their valves. There may not be enough material thickness in their design for the parts to be strong enough to withstand the higher pressures.

It is not tht the material is "soft". The modulus of elasticity is essentially the same as other steels, so until the stress exceeds the material yield, the amount of deformation is roughly the same. Unless it is strain hardened, 316 / CF8M has a lower yield strength than 400 series steels that are commonly used for high pressure valve trim parts such as balls and stems.

 

[SNORGY]

It is an ESD valve, so it is either open or closed or on its way between the two states. Some high velocity wet or solids-laden flow might scratch up the port, but in high pressure flow, unless you are going straight to a low pressure system with no intervening choke downstream of the ESD, I suspect you won't be seeing much erosion in the ESD itself. In the closed position you shouldn't be seeing any erosion on the outside of the ball, since there is no flow in that position.

I think their concern might be abrasion on the ball in a dirty service when it rotates from open to closed or vice versa, causing it to lose its ability to seal over time.